The present invention relates to rotary kilns, and more particularly to an air conveying system for the introduction of port air into the bed of material being processed in a rotary kiln.
In currently utilized ported rotary kilns, the rotary kiln includes a series of openings extending through the refractory lining and outer shell to allow air to enter into the kiln to enhance the process occurring within the kiln. Typically, the series of openings each include a metal grid that is flush mounted with the inner surface of the kiln refractory lining, as is shown in U.S. Pat. No. 5,248,330. Although this type of grid is effective to prevent large particles of material from entering into the duct work introducing the air, the grid is directly exposed to both the high temperature and the hot tumbling material within the open enclosure of the rotating kiln. The high temperature and the physical contact with the tumbling material causes wear to the grid, which must eventually be replaced.
Additionally, the grid size of the flush mounted grid of the prior art allows small particles of material to enter into the duct work. These small particles can eventually plug the duct work causing a reduction or total loss of port air flow. If for any reason there is a loss of port air, the metal grid will quickly melt due to contact with the hot tumbling material within the kiln.